Defendant

wiktionary

ref

From Middle English defendaunt(“defending; defending in a suit”), borrowed from Old French defendant, present participle of defendre, from Latin dēfendere.

From Middle English defendaunt(“defendant in a suit; defender”), borrowed from Old French defendant, nominalisation of defendant; see above.

etymonline

ref

defendant (n.)

c. 1400, in the legal sense "a party sued in a court of law," from Anglo-French, Old French defendant (Modern French défendant), noun use of present participle of defendre (see defend). Earliest use in English was as a present-participle adjective meaning "defensive, defending" (c. 1300).